Quotewodcutr
So what you are saying is that because there are no knock sensors in our motors the ECU does not adjust the fuel mixture or retard the timing. I believe it does, just not to the extent that a more modern engine would. What I am getting at is that our computers certainly do have the capability of adjusting fuel consumption for better or worse economy based on the input from the O2 sensor. Too rich and it leans out the mixture increasing mileage. Higher octane fuel does make the mixture richer does it not?

The first problem is that these cars (from the factory) were designed to run on regular. That means that at it's ideal tune, it does not require higher octane fuel to prevent detonation. Certainly it might be able to adjust enough to induce detonation, but it won't because it will be detrimental to the engine's performance.

Second, no, higher octane fuel will not make the mixture richer. Both grades of fuel contain nearly the same amount of energy. Check out this article, and this one too.

Quotewodcutr
Dave - the idea here is to not give the motor an opportunity to knock. If your motor starts knocking then there is damage being done. Most people have their music turned up loud and would be totally oblivious as to whether or not the motor is knocking. I will admit that the higher the temp outside the greater the probability for knocking so winter is not totally necessarily premium time. As far as my high compression snowmobile motor burning up not being a relative matter, I say that the high compression had nothing to do with melting the piston and it had everything to do with a fuel mixture being too lean. A higher octane fuel not only burns cooler but also cleaner and helps disperse the heat better within the combustion chamber. There is a difference between 85 and 91 octane fuel. The computer has to adjust to burn each one properly. If there wasn't a difference then why make premium? I guess it is just another ploy that the oil companies use to sucker us for a few bucks more. I don't think so. If you want better performance from your motor use premium. The computer adjusts to give you better performance. As far as you testing for better mileage it needs to be done for at least a month so you can average out your dally trips better. One tank will not give you much of anything as your computer is still adjusting during that time frame. I know you think I am a fool discussing this matter. I have read many such discussions from the old BEN forum and I can only tell you that this is my personal experience. I could be wrong, but I can not argue against what the past has shown me. If I did, I would go insane. That is the difference between knowledge and wisdom. Experience is everything. I am of the mindset that prevention of a problem is better than treating symptoms. Knocking is a symptom...91 octane fuel is prevention!

If running the high octane fuel makes you feel better about things, fine, its a personal choice... and it might work for you B)

Quotewodcutr
So what you are saying is that because there are no knock sensors in our motors the ECU does not adjust the fuel mixture or retard the timing. I believe it does, just not to the extent that a more modern engine would. What I am getting at is that our computers certainly do have the capability of adjusting fuel consumption for better or worse economy based on the input from the O2 sensor. Too rich and it leans out the mixture increasing mileage. Higher octane fuel does make the mixture richer does it not?

The first problem is that these cars (from the factory) were designed to run on regular. That means that at it's ideal tune, it does not require higher octane fuel to prevent detonation. Certainly it might be able to adjust enough to induce detonation, but it won't because it will be detrimental to the engine's performance.

Second, no, higher octane fuel will not make the mixture richer. Both grades of fuel contain nearly the same amount of energy. Check out this article, and this one too.

I guess you can call me eccentric then, only because my car is chipped...I need premium. I certainly do not use premium in my other vehicles.

OK, so if premium does not richen the fuel mixture does it burn cleaner or do something to tell the ECU (O2 sensor input) it can adjust so you get better mileage? IMO there has to be a logical explanation for my getting the mileage I do. Is it the chip? I know that some chip makers claim that their chip will increase mileage. Could it be that the increased HP means that you don't need to press the gas pedal as much to maintain a certain speed? I don't drive like an old man either. I put down the go pedal all the time, especially if I am in pole position at a light.

As far as my snowmobile motor is concerned I also need to know if my understanding of what took place is correct. The race fuel has to do something for that motor that 91 octane fuel can't. The Polaris dealer told me that melting the piston was indicative of the mixture being too lean. If a higher octane fuel could have prevented that, then wouldn't that mean that the higher octane fuel richens the mixture? And how does a lean mixture produce higher heat...enough to melt a small portion of the piston? Fixing that motor is costing a lot of money. I don't want it to happen again if it can be helped!

Quotewodcutr
OK, so if premium does not richen the fuel mixture does it burn cleaner or do something to tell the ECU (O2 sensor input) it can adjust so you get better mileage? IMO there has to be a logical explanation for my getting the mileage I do. Is it the chip? I know that some chip makers claim that their chip will increase mileage. Could it be that the increased HP means that you don't need to press the gas pedal as much to maintain a certain speed? I don't drive like an old man either. I put down the go pedal all the time, especially if I am in pole position at a light.

This is the idea I have with chips. It changes the powerband in order to use fuel more effectively (the increase in power). This could be wrong, though.

Quotedwonda
Well unless you've dyno'd your car I guess you don't know what your actual HP gain from a chip is, and I think it would be more fair to compare your car to a chipped 328iS, I would never do it because I don't want to pay for premium gasoline, or even gasoline additives to make it a higher octane. I wasn't trying to convince anyone that an E36 was better, but I have a problem with someone saying an E30 is who hasn't driven an E36. Tell me more about your car that you say you might be able to let go

My car has not been dyno'd, but I think that a reputable chip maker like Dinan wouldn't lie about their chip and publish false numbers of cars they did dyno. Besides the HP gain is only 15 so IMO that is pretty conservative compared to what other chips claim. As far as paying for premium fuel I believe you should be putting that in anyway, especially in the summer and on a higher mileage engine. I think that for three extra dollars per fill up it is worth it...skip the coffee for a day and invest in something good for your car. Also, I do not think you would be interested in any of my E30s so I won't waist my breath or time telling you about them. It sounds to me that you are convinced the 328 is the way to go and I support you in your endeavour. I am curious as to why you have two user names - dwonda and Andrew? Am I talking to the same person?

dwonda has a point. the 328is is only has 193hp. as you mentioned, it weighs more, so your car with a chip might have around 180hp (lets not try to account for mileage on each motor, etc) and probably wouldn't have any trouble keeping up with the e36. there is also the issue of gearing. automatic/manual, along with the differential ratio. probably the same reason why my e30 318is (not chipped) beat an e46 325i.

wodcutr, you seem to have a great disdain for anyone who mouths the word e36. this is a public forum, and while you can choose to antagonize those who prefer an e36 for whatever reason, to me you are coming off as rude and a bit stubborn, unwilling to accept that someone might enjoy the e36 more and for different reasons. i hope that for the pleasantry of this forum you reconsider the way you respond to those with an affinity for the e36.

also, it is silly to accuse andrew of creating another user name in order to respond to your question.

Engines with knock sensors advance spark all the time, until the sensor detects (just slight) knock. Then it retards spark and advances it again, gradually. These engines knock once in a while, just for a very short time. Changing octane grade will not change the amount of knock in these engines, it will only shift the spark timing window.

wodcutr, you seem to have a great disdain for anyone who mouths the word e36. this is a public forum, and while you can choose to antagonize those who prefer an e36 for whatever reason, to me you are coming off as rude and a bit stubborn, unwilling to accept that someone might enjoy the e36 more and for different reasons. i hope that for the pleasantry of this forum you reconsider the way you respond to those with an affinity for the e36.

also, it is silly to accuse Andrew of creating another user name in order to respond to your question.

thanks

Daniel - I am sorry if it seems to you that I am rude and stubborn. I do like to argue my opinions and am not known for my political correctness. That being said, I have stated several times that I like the way the E36 looks and even thought that the E36 was a more refined car. To some it may even be a better car for them and I do not have a problem with anyone owning one or thinking that their car is better. That is their choice and right to think. I have thought several times of looking into purchasing one for myself. I guess I am just too brash and unrefined for you and others to accept here. I find it interesting that one such as yourself cannot differentiate between playful ribbing and serious confrontation. I suppose in the future I will have to indicate on all my posts that I am joking around by using more smileys. I guess I am just new at this blog stuff and do not know the proper etiquette to use. I will try to use more restraint in my posts. Thanks for your input!

As far as my accusing Andrew of having two user names, I was only trying to figure out if for some reason Andrew was responding as dwonda because I was having a discussion with Andrew who did not seem too offended by what I had to say and responded directly to me in his posts. Then came along dwonda who acted as if he were Andrew continuing that conversation. It was just weird IMO. Maybe I'm the weird one! I also find it interesting that neither one has responded to the question. I guess I have single handedly run off all the E36 owners using this forum. I apologise and hope they come back for everyone else's sake. Maybe I should be punished in some way. You can demote me to newbie again if you feel so inclined. Maybe I should create a new user name and just start over. I know - wodcutr can be Dr Jekyll and the new guy can be Mr Hyde. Then I can be the one with two user names and be able to have conversations with myself. :thinking: Can you tell that I have not worked in over a year...I think I am loosing it!

QuoteMichiel 318iS
Engines with knock sensors advance spark all the time, until the sensor detects (just slight) knock. Then it retards spark and advances it again, gradually. These engines knock once in a while, just for a very short time. Changing octane grade will not change the amount of knock in these engines, it will only shift the spark timing window.

So if I understand correctly what you have stated, an older engine that has worn parts and lesser tolerances would be more prone to knocking and thus more likely to get worse fuel economy because the spark will most likely be retarded.

They are only "more prone" in the sense that they won't automatically retard the timing to account for it. Tolerances have nothing to do with it, in fact, just the opposite case could be made. If tolerances were lousy and you were losing compression, fuel would be LESS likely to detonate early.

QuoteAndy 90 325i
They are only "more prone" in the sense that they won't automatically retard the timing to account for it. Tolerances have nothing to do with it, in fact, just the opposite case could be made. If tolerances were lousy and you were losing compression, fuel would be LESS likely to detonate early.

I guess loss of compression would mean knocking is less likely. Greater tolerances would certainly allow piston slap though...nothing the computer can do about that!

wodcutr, you seem to have a great disdain for anyone who mouths the word e36. this is a public forum, and while you can choose to antagonize those who prefer an e36 for whatever reason, to me you are coming off as rude and a bit stubborn, unwilling to accept that someone might enjoy the e36 more and for different reasons. i hope that for the pleasantry of this forum you reconsider the way you respond to those with an affinity for the e36.

also, it is silly to accuse Andrew of creating another user name in order to respond to your question.

thanks

Daniel - I am sorry if it seems to you that I am rude and stubborn. I do like to argue my opinions and am not known for my political correctness. That being said, I have stated several times that I like the way the E36 looks and even thought that the E36 was a more refined car. To some it may even be a better car for them and I do not have a problem with anyone owning one or thinking that their car is better. That is their choice and right to think. I have thought several times of looking into purchasing one for myself. I guess I am just too brash and unrefined for you and others to accept here. I find it interesting that one such as yourself cannot differentiate between playful ribbing and serious confrontation. I suppose in the future I will have to indicate on all my posts that I am joking around by using more smileys. I guess I am just new at this blog stuff and do not know the proper etiquette to use. I will try to use more restraint in my posts. Thanks for your input!

As far as my accusing Andrew of having two user names, I was only trying to figure out if for some reason Andrew was responding as dwonda because I was having a discussion with Andrew who did not seem too offended by what I had to say and responded directly to me in his posts. Then came along dwonda who acted as if he were Andrew continuing that conversation. It was just weird IMO. Maybe I'm the weird one! I also find it interesting that neither one has responded to the question. I guess I have single handedly run off all the E36 owners using this forum. I apologise and hope they come back for everyone else's sake. Maybe I should be punished in some way. You can demote me to newbie again if you feel so inclined. Maybe I should create a new user name and just start over. I know - wodcutr can be Dr Jekyll and the new guy can be Mr Hyde. Then I can be the one with two user names and be able to have conversations with myself. :thinking: Can you tell that I have not worked in over a year...I think I am loosing it!

you can be as brash and unrefined as you want. i just sensed some aggressive replies when there wasnt any aggression from the other end to warrant them. i am sure you were not intending that tone so you probably werent aware of it. i only wanted to make you aware. i think dwonda was just contributing to the discussion between the e30 and e36, not necessarily trying to act like Andrew.

i am not going to demote you. in fact, the only reason i am a moderator is to clean the forum of spam, move a thread if someone asks, and to make a sticky now and then. i never intend to moderate any posts.

Quotewodcutr
So what you are saying is that because there are no knock sensors in our motors the ECU does not adjust the fuel mixture or retard the timing. I believe it does, just not to the extent that a more modern engine would. What I am getting at is that our computers certainly do have the capability of adjusting fuel consumption for better or worse economy based on the input from the O2 sensor. Too rich and it leans out the mixture increasing mileage. Higher octane fuel does make the mixture richer does it not?

The first problem is that these cars (from the factory) were designed to run on regular. That means that at it's ideal tune, it does not require higher octane fuel to prevent detonation. Certainly it might be able to adjust enough to induce detonation, but it won't because it will be detrimental to the engine's performance.

Second, no, higher octane fuel will not make the mixture richer. Both grades of fuel contain nearly the same amount of energy. Check out this article, and this one too.

I guess you can call me eccentric then, only because my car is chipped...I need premium. I certainly do not use premium in my other vehicles.

OK, so if premium does not richen the fuel mixture does it burn cleaner or do something to tell the ECU (O2 sensor input) it can adjust so you get better mileage? IMO there has to be a logical explanation for my getting the mileage I do. Is it the chip? I know that some chip makers claim that their chip will increase mileage. Could it be that the increased HP means that you don't need to press the gas pedal as much to maintain a certain speed? I don't drive like an old man either. I put down the go pedal all the time, especially if I am in pole position at a light.

It is quite possible that you are getting better mileage than other 'chipped' car-drivers, but I don't think that you are getting better mileage than a non-chipped 20, since you are claiming more HP. More HP for the same engine using ONLY a chip to extract that HP, means LESS mileage. However, you could be getting better mileage than other chipped versions because you are NOT getting more HP, but a better management of the original engine. That being siad, I am always sceptical of mileage claims, since not many people really know how to really calculate proper mileage figures and do the math to properly analyse the data to make any valid conclusions as to significant differences in the figures.

As far as my snowmobile motor is concerned I also need to know if my understanding of what took place is correct. The race fuel has to do something for that motor that 91 octane fuel can't. The Polaris dealer told me that melting the piston was indicative of the mixture being too lean. If a higher octane fuel could have prevented that, then wouldn't that mean that the higher octane fuel richens the mixture? And how does a lean mixture produce higher heat...enough to melt a small portion of the piston? Fixing that motor is costing a lot of money. I don't want it to happen again if it can be helped!

The issues of octane and fuel mixture 'richness' are totally unrelated, except for reaction temperatures. You melted your pistons because the ratio was too lean and you would have melted the pistons even if you had been using the 'higher octane' fuel. Up to point the leaner the mixture the higher the temperature of the reaction and its resulting product gases, since there is less mass to absorb the enrgy produced. Detonation (pinging) can also destroy an engine, as Ferdinand has well described and possibly that is what hurt your snowmobile engine, not fuel mixture, and using a higher than specified octane fuel might mitigate that situation. If that is the case, then I would ask why your engine needs higher than specified octane fuel. I would speculate that you have carbon deposits in the engine or some modifications have been made, effectively increasing the compression ratio. BTW, over richening the fuel mixture is another way to prevent detonation, since that cools the reactants temperatures, therefore reducing the propensity to 'pre-ignite'.

Finally Bob has chimed in. My snowmobile motor is highly modified. The head can be adjusted up or down to vary the compression ratio. My question is: can detonation melt a piston? I have been told several times that the race fuel added to my tank allows the fuel mixture to burn cooler thus giving that motor a little more cushion so to speak. If that is not really the case then I need to richen the mixture by increasing the jet size in the carbs or it will burn down again. Also wondering what the signs would be inside the motor indicative of that detonation? I was also told that outside temperatures and elevation contributed to this meltdown. What say you?

Let's clear up one thing immediately. Higher octane fuel DOES NOT burn cooler. I don't know how your mechanic came up with the diagnosis that your piston melted due to a lean mixture, since the symptoms of detonation damage to pistons and lean fuel damage to pistons are very similar.
For racing, using a richer mixture is the way to go, unless mileage is important, since there is less possibility of detonation and high temperatures. Of course, using a rich mixture and higher octane will do no harm, but there is no HP advantage.

Salut, Bob P.

PS. if you find that my messages are missing 'm's, that is because I a having problems with the M on my keyboard!

Quotewodcutr
I was also told that outside temperatures and elevation contributed to this meltdown. What say you?

Sorry, I missed this in my previous answer. Higher elevations will enrih the mixture IF there is no computer to calculate the actual mass of air, since its density is lower at elevations. Higher temperatures (of the air) will increase the propensity of detonation due to the higher temperature of the reactants, especially if one is very close to detonation.

Good points but just remember that being a moderator means you have to check all biases, sensitivities and prejudices at the door.
Seems like you are the only one that found anything out of order here...

Also; since you didn't read my reply and you weren't around early enough to know, Andrew aka dwonda...jumanji...etal is an old and established member of BEN.
His E30 bimmerhood educated many of us about the things that good mechanics do and also some of the weirdness that BMW has done.

We're all cool here and had you been around; you would know how much Andrew hurt when he had to trash his E30.

QuoteArcheo-peteriX
Good points but just remember that being a moderator means you have to check all biases, sensitivities and prejudices at the door.
Seems like you are the only one that found anything out of order here...

Also; since you didn't read my reply and you weren't around early enough to know, Andrew aka dwonda...jumanji...etal is an old and established member of BEN.
His E30 bimmerhood educated many of us about the things that good mechanics do and also some of the weirdness that BMW has done.

We're all cool here and had you been around; you would know how much Andrew hurt when he had to trash his E30.

i was trying to reply to him/express concern from a fellow user standpoint, not from a moderator standpoint. the only reason i brought that up is because he talked about being demoted.